This question comes up quite frequently in the form of "What benefit do I get from using a more complicated mash schedule than single temperature infusion?".

Mashing needs to be seen as an extension of the malting process and what wasn't done during the malting of the grain, needs to be done during mashing. And the more modified a malt is, the fewer mashing steps are necessary to produce a wort suitable for brewing a quality beer. Even worse, by selecting a more intense mashing schedule for a highly modified malt certain steps, like protein conversion, can be overdone and lead to a less optimal wort composition.

Here is a list of some malts showing mashing schedules that work well for them:

Infusion mashing is the process of achieving your mash temperatures by adding measured amounts of water heated to carefully calculated temperatures to the mash.

In a single infusion mash, the mash water is added all at once and the mash is held at a single steady temperature for the entire mash. In a step infusion mash, some of the water is held back and heated then be added to the main mash to raise the temperature to each additional step. In either case, an insulated mash tun, such as a converted picnic cooler mash tun, is used to keep the temperature steady without the need for direct heat.

Directly heating the mash to maintain or adjust temperature can result in scorching and cause compounds that add off flavors to the beer. Direct heat can also de-activate enzymes causing incomplete starch conversion in mashes with marginal diastatic power. A decoction can be used to raise the mash temperature.

In decoction mashing the temperature of the mash is increased by removing a part of the mash, bringing it to a boil and returning it to the main mash. Decoction mashes are categorized by the number of decoctions that are pulled, boiled and returned: